Field of the Invention
The present disclosure relates to a coloring compound and a thermal transfer recording sheet.
Description of the Related Art
In recent years, with the widespread use of portable color display devices, the demand for easy color printing of photographs taken and documents prepared with the devices has been increasing. Examples of a color-printing method that meets the demand include an electrophotographic method, an ink-jet method, and a thermal transfer recording method. The thermal transfer recording method enables printing by a dry process and miniaturization of a printer, thereby providing excellent portability. Thus, of the foregoing methods, the thermal transfer recording method is excellent due to easy printing in any environment. In addition, since this method uses a dye as a coloring material, density of an image can be controlled by using a concentration gradient of coloring materials, thereby resulting in clear images and excellent color reproducibility.
The thermal transfer recording method is an image forming method that includes placing a thermal transfer recording sheet on an image-receiving sheet and heating the thermal transfer recording sheet to transfer a coloring agent present in the thermal transfer recording sheet onto the image-receiving sheet. The thermal transfer recording sheet includes, on a sheet-shaped base material, a coloring-material layer containing a coloring agent that has heat-transfer properties. The image-receiving sheet includes a coloring-agent-receiving layer on a surface thereof. In the thermal transfer recording method, the coloring material contained in the coloring-material layer affects the speed of transfer recording, recorded image quality, and storage stability, and thus, it is a very important material.
Such a thermal transfer recording method uses ink sheets each containing a yellow dye, a magenta dye, or a cyan dye as a coloring material to produces images. Even if the use of a single dye for producing images provides sufficient lightfastness, the use of different dyes in combination for producing images may cause the phenomenon of poor lightfastness (Japanese Patent Laid-Open No. 2007-290343). This phenomenon is called catalytic fading, which occurs particularly in a mixture of a yellow dye and a cyan dye.